1. Field of the Invention
The present invention relates to a keyboard for electronic equipment, and more particularly to a keyboard switch having a planar switch actuator.
2. Description of the Prior Art
A prior art keyboard switch of this type is shown in FIGS. 1 and 2, and has a main body 1 a decoration sheet 2, a frame 3, and a printed circuit board 4. The decoration sheet 2 and the frame 3 are bonded together by bond 5 as shown in FIG. 2, and the frame 3 and the printed circuit board 4 are fixed to each other by bond or bolts. As shown in FIG. 2, an opening is formed in the frame 3 under a key symbol marked on the decoration sheet 2 and a disc 8 of an elastic metal drawn into a dome shape is disposed in the opening to contact lead terminals 6 which are held in the frame 3. An upper surface of the disc 8 abuts against a projection 7 formed on the lower surface of the decoration sheet 2. A movable contact 9 is formed on the lower surface of the disc 8 and a stationary contact 10 is formed on the printed circuit board 4 below the movable contact 9.
When the upper surface of the key symbol of the decoration sheet 2 is depressed by a finger or an actuating rod in a direction of an arrow shown in FIG. 3, the decoration sheet 2 extends downwardly and the projection 7 presses the disc 8. As a result, the disc 8 is flexed downwardly as shown in FIG. 3. By the flexure of the disc 8, a feeling of a click is imparted and the movable contact 9 contacts the stationary contact 10 of the printed circuit board 4 so that a key input signal corresponding to the key symbol is produced.
In the prior art keyboard switch described above, the switch is actuated by the downward extension of the decoration sheet 2 by the depression. Accordingly, the decoration sheet 2 must be made of a material having a large extensibility. However, since material having large extensibility has a relatively low hardness, the decoration sheet 2 is readily scratched by a nail of a finger or a tip end of a rod when the switch is actuated. Further, because of the requirement of large extensibility, a scope of selection of the material of the decoration sheet is limited. Since the key symbol indicating the key function has to be printed on the decoration sheet, the manufacture of the decoration sheet is time-consuming and expensive.